fix typo

mllib/src/main/scala/org/apache/spark/ml/feature/RFormula.scala

@@ -38,33 +38,35 @@ import org.apache.spark.sql.types._
 private[feature] trait RFormulaBase extends HasFeaturesCol with HasLabelCol {
 
   /**
-   * Param for how to order categories of a FEATURE string column used by `StringIndexer`.
+   * Param for how to order categories of a string FEATURE column used by `StringIndexer`.
    * The last category after ordering is dropped when encoding strings.
-   * The options are explained using an example string: 'b', 'a', 'b', 'a', 'c', 'b'
-   * {{{
-   * +-----------------+---------------------------------------+---------------------------------+
-   * |      Option     | Category mapped to 0 by StringIndexer |  Category dropped by RFormula   |
-   * +-----------------+---------------------------------------+---------------------------------+
-   * | 'frequencyDesc' | most frequent category ('b')          | least frequent category ('c')   |
-   * | 'frequencyAsc'  | least frequent category ('c')         | most frequent category ('b')    |
-   * | 'alphabetDesc'  | first alphabetical category ('a')     | last alphabetical category ('c')|
-   * | 'alphabetAsc'   | last alphabetical category ('c')      | last alphabetical category ('a')|
-   * +-----------------+---------------------------------------+---------------------------------+
-   * }}}
+   * Supported options: 'frequencyDesc', 'frequencyAsc', 'alphabetDesc', 'alphabetAsc'.
    * The default value is 'frequencyDesc'. When the ordering is set to 'alphabetDesc', `RFormula`
    * drops the same category as R when encoding strings.
+   *
+   * The options are explained using an example `'b', 'a', 'b', 'a', 'c', 'b'`:
+   * {{{
+   * +-----------------+---------------------------------------+----------------------------------+
+   * |      Option     | Category mapped to 0 by StringIndexer |  Category dropped by RFormula    |
+   * +-----------------+---------------------------------------+----------------------------------+
+   * | 'frequencyDesc' | most frequent category ('b')          | least frequent category ('c')    |
+   * | 'frequencyAsc'  | least frequent category ('c')         | most frequent category ('b')     |
+   * | 'alphabetDesc'  | first alphabetical category ('a')     | last alphabetical category ('c') |
+   * | 'alphabetAsc'   | last alphabetical category ('c')      | first alphabetical category ('a')|
+   * +-----------------+---------------------------------------+----------------------------------+
+   * }}}
    * Note that this ordering option is NOT used for the label column. When the label column is
    * indexed, it uses the default descending frequency ordering in `StringIndexer`.
    *
    * @group param
    */
   @Since("2.3.0")
   final val stringIndexerOrderType: Param[String] = new Param(this, "stringIndexerOrderType",
-    "How to order categories of a FEATURE string column used by StringIndexer. " +
+    "How to order categories of a string FEATURE column used by StringIndexer. " +
     "The last category after ordering is dropped when encoding strings. " +
+    s"Supported options: ${StringIndexer.supportedStringOrderType.mkString(", ")}. " +
     "The default value is 'frequencyDesc'. When the ordering is set to 'alphabetDesc', " +
-    "RFormula drops the same category as R when encoding strings." +
-    s"Supported options: ${StringIndexer.supportedStringOrderType.mkString(", ")}.",
+    "RFormula drops the same category as R when encoding strings.",
     ParamValidators.inArray(StringIndexer.supportedStringOrderType))
 
   /** @group getParam */